It's written everywhere that anomalistic month orbits 360 degrees completely, then how many degrees does the sidereal month orbit?

Here is written that the sidereal month orbits 360 degrees too, but it doesn't make sense that they have the same orbit degrees since the anomalistic month is longer.

According to my logic, if 360 degrees equal to 27.55455 days, then 27.321661 days (=sidereal month) equal to 356.9 degrees, rather than 360 degrees. Is it correct?

  • $\begingroup$ Your logic is incorrect. Please accept @MikeG's answer as it is correct. $\endgroup$ Apr 19 '20 at 11:58
  • $\begingroup$ No problem. I'm just looking for reference who says it. Once I find it, I'll accept it. $\endgroup$ Apr 19 '20 at 12:28
  • 2
    $\begingroup$ Nowhere reputable is it written that in an anomalistic month the Moon orbits 360 degrees completely. Nowhere. $\endgroup$ Apr 19 '20 at 12:56

The Moon does move 3.1° in the 0.23 day difference between those month lengths, but it goes 360° in a sidereal month and 363.1° in an anomalistic month.

The anomalistic month, from perigee to perigee, is slightly longer because the perigee moves. The lunar apsides take 8.85 years to go all the way around the circle.

Similiarly, the draconic month is slightly shorter because the nodes move the other way in a cycle of 18.6 years.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.